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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

On the nature of the material surrounding Vega

Observations of Vega at 193 microns indicate that the far-infrared emission from the circumstellar material discovered by IRAS (Aumann et al. 1984) may decline more rapidly than a Planck spectrum at wavelengths greater than 100 microns. This suggests that the emitting particles may be smaller than the millimeter-sized objects proposed by Aumann et al. (1984). Small grains would be driven from the stellar system by radiation pressure, or their orbits would decay as a result of Poynting -Robertson drag. In order to maintain a state of dynamic equilibrium, a continuous supply of new particles would be required. It is hypothesized that the small grains are ejected by sublimation of volatile material from larger comet-like bodies in a partially coalesced preplanetary disk. A reservoir containing less than a few hundred earth masses could sustain the source over the lifetime of the star.

Harper, D. A.↗
NASA NTRS1995

Observations and analysis of O(1D) and NH2 line profiles for the coma of comet P/Halley

A set of high-resolution Fabry-Perot measurements of the coma of comet P/Halley was acquired in the (O I) 6300 A and NH2 6298.62 A emission lines. These high-resolution measurements provide the first optical observations capable of studying directly the photochemical kinetics and dynamic outflow of the coma. The observations were analyzed by a Monte Carlo Particle Trajectory Model. The agreement of the model and observed line profiles was excellent and verified the underlying dynamics, exothermic photodissociative chemistry, and collisional thermalization in the coma. The somewhat wider intrinsic line profile width for the O(1D) emission in 1986 January compared to 1986 May, is, for example, produced by the larger outflow speeds and gas temperatures nearer perihelion in January. The January O(1D) profile, which is wider than the January NH2 profile, is indicative of the photochemical kinetics in the dissociation of the parent molecules H2O and OH in the coma. The absolute calibration of the observations in 1986 January allowed the production rates for H2O and the NH2-parent molecules to be determined. The average daily water production rates derived from the O(1D) emission data for January 16 and 17 are presented. These very large water production rates are consistent with the extrapolated (and 7.6 day time variable) water production rates determined from the analysis of lower spectral resolution observations for O(1D) and H-alpha emissions that covered the time period up to January 13. The large production rates on January 16 and 17 establish that the maximum water production rate for comet Halley accurred pre-perihelion in January. Implications drawn from comparison with 18 cm radio emission data in January suggest that the peak water production rate was even larger. The average production rate for NH3 determined from the NH2 emission data for January 17 was (1.48 +/- 0.10) x 10(exp 28) molecules/s, yielding an NH3/H2O production rate ratio of 0.55%.

Smyth, William H.↗
NASA NTRS1994

Tidal disruption and the appearance of periodic comet Shoemaker-Levy 9

A unified model is formulated to interpret quantitatively the observed characteristics of the nuclear train, the two dust trails, and the tail region of P/Shoemaker-Levy 9 in terms of a collisionally modified rotation velocity distribution of the comet's debris. Since there is no evidence for the comet's out-gassing, the model does not assume activity. The discruption of the parent comet was due primarily to tidal stesses during its extremely close approach to Juptier in July 1992. The original nucleus is found to have been most probably approximately 5 km in radius or, equivalently, approximately 10(exp 17) g in mass. The dynamical separation of the debris occurred apparently approximately 2.2 hr after the perijove passage, even though the actual fragmentation of the original mass is likely to have begun before closest approach. Physical breakp was accompanied by ubiquitous low-velocity collisions among the particulates, resulting in a rearrangement of the initial rotaional velocities into a rapidly 'thermalized' distribution, characterized by a long tail of relatively high velocities for the debris that populates the dust trails far from the nuclear train. Compelling evidence is presented for secondary fragmentation events, indicative of the comet's continuing disintegration. Secondary fragmentation may be caused by rotational bursting of the massive fragments that had been cracked but unbroken during the tidal disruption. Impact conditions and possible interactions of the comet's debris with the jovian system during the encounter in July 1994 are described.

Sekanina, Z.↗
NASA NTRS1977

Planetary astronomy program

A program was developed in which asteroids and two planets, namely, Saturn and Uranus, were investigated. This included: (1) asteroid spectrophotometry; (2) the nature of the Trojan asteroids; (3) an investigation to determine asteroid masses; (4) the photometry, structure, and dynamics of the rings surrounding the planet Saturn; and (5) aerosol distribution in the atmosphere of Uranus. Plans were finalized to obtain observations of the nucleus of the dying comet P/Arend-Rigaux. Further work was accomplished in asteroid data reduction. Data were entered into the TRIAD data file and a program generated classifications for over 560 different asteroids. A photoelectric area scanner was used to obtain UBV scans of the disk of the planet Saturn on several winter and spring nights in 1977. Intensity profiles show pronounced limb brightening in U, moderate limb brightening in B, and limb darkening in V. Narrow band photoelectric area-scanning photometry of the Uranus disk is also reported. Results are given.

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NASA NTRS2009

Investigation of Phase Transition-Based Tethered Systems for Small Body Sample Capture

This paper summarizes the modeling, simulation, and testing work related to the development of technology to investigate the potential that shape memory actuation has to provide mechanically simple and affordable solutions for delivering assets to a surface and for sample capture and possible return to Earth. We investigate the structural dynamics and controllability aspects of an adaptive beam carrying an end-effector which, by changing equilibrium phases is able to actively decouple the end-effector dynamics from the spacecraft dynamics during the surface contact phase. Asset delivery and sample capture and return are at the heart of several emerging potential missions to small bodies, such as asteroids and comets, and to the surface of large bodies, such as Titan.

deployable systems↗
NASA NTRS2011

Surface Contact Model for Comets and Asteroids

A contact force model was developed for use in touch and go (TAG) surface sampling simulations on small celestial bodies such as comets and asteroids. In TAG scenarios, a spacecraft descending toward the surface of a small body comes into contact with the surface for a short duration of time, collects material samples with a sampler device, and then ascends to leave the surface. The surface contact required 6-DOF (degrees of freedom) dynamics models due to coupling of the attitude and translation dynamics during the contact. The model described here is for contact scenarios that utilize a rotating brush wheel sampler (BWS) to collect surface material. The model includes stiffness and damping of the surface material during BWS vertical motion, lateral friction from the BWS dragging across the surface, and lateral shear from the rotating BWS scooping the surface material. This model is useful for any mission to asteroids or comets that incorporates surface sampling operations.

Blackmore, Lars James C.↗
NASA NTRS1992

On LAM's and SAM's for Halley's rotation

Non principal axis rotation for comet Halley is inferred from dual periodicities evident in the observations. The modes where the spin axis precesses around the axis of minimum moment of inertia (long axis mode or LAM) and where it precesses around the axis of maximum moment of inertia (short axis mode or SAM) are described from an inertial point of view. The currently favored LAM model for Halley's rotation state satisfies observational and dynamical constraints that apparently no SAM can satisfy. But it cannot reproduce the observed post perihelion brightening through seasonal illumination of localized sources on the nucleus, whereas a SAM can easily produce post or pre perihelion brightening by this mechanism. However, the likelihood of a LAM rotation for elongated nuclei of periodic comets such as Halley together with Halley's extreme post perihelion behavior far from the Sun suggest that Halley's post perihelion brightening may be due to effects other than seasonal illumination of localized sources, and therefore such brightening may not constrain its rotation state.

Peale, Stanton J.↗
NASA NTRS2006

LAD-C: A large area debris collector on the ISS

The Large Area Debris Collector (LAD-C) is a 10 sq m aerogel and acoustic sensor system under development by the U.S. Naval Research Laboratory (NRL) with main collaboration from the NASA Orbital Debris Program Office at Johnson Space Center, JAXA Institute of Space and Astronautical Science (ISAS), Chiba University (Japan), ESA Space Debris Office, University of California at Berkeley, and University of Kent at Canterbury (UK). The U.S. Department of Defense (DoD) Space Test Program (STP) has assumed the responsibility for having the system manifested and deployed on the International Space Station (ISS), and then having it retrieved and returned to Earth after one to two years. LAD-C will attempt to utilize the ISS as a scientific platform to characterize the near-Earth meteoroid and orbital debris environment in the size regime where little data exist. In addition to meteoroid and orbital debris sample return, the acoustic sensors will record impact time, location, signal strength, and acoustic waveform data of the largest collected samples. A good time-dependent meteoroid and orbital debris flux estimate can be derived. Analysis of the data will also enable potential source identification of some of the collected samples. This dynamical link can be combined with laboratory composition analysis of impact residuals extracted from aerogel to further our understanding of orbital debris population, and the sources of meteoroids, asteroids and comets.

Liou, J.-C.↗
NASA NTRS1976

Investigation of interplanetary dust from out-of-ecliptic space probes

Measurements of interplanetary dust via zodiacal light observations and direct detection are discussed for an out-of-ecliptic space probe. Particle fluxes and zodiacal light brightnesses were predicted for three models of the dust distribution. These models predict that most of the information will be obtained at space probe distances less than 1 A.U. from the ecliptic plane. Joint interpretation of the direct particle measurements and the zodiacal light data can yield the best knowledge of the three-dimensional particle dynamics, spatial distribution, and physical characteristics of the interplanetary dust. Such measurements are important for an understanding of the origin and role of the dust in relation to meteoroids, asteroids, and comets, as well as the interaction of the dust with solar forces.

Fechtig, H.↗
NASA NTRS2019

Observations of Jupiter Family Comet 252P/LINEAR During a Close Approach to Earth Reveal Large Abundances of Methanol and Ethane

We observed short-period comet 252P/LINEAR post-perihelion during its 2016 passage, which presented a favorable opportunity to survey its chemical composition at a close Earth approach (∼0.14 au). We characterized the comet’s chemical composition on four dates (UT 2016 April 12, 19, 26, and 29) using spectroscopic measurements with the Near-infrared Spectrograph (NIRSPEC) at the Keck Observatory on Maunakea, HI. Our high-resolution infrared spectra yielded production rates for four species (H2O, CH3OH, C2H6, and HCN) and upper limits for five species (NH3, H2CO, C2H2, CO, and CH4). We measured water at an average production rate of 4.9 ± 0.1 × 10(exp 27) molec s(exp -1). The chemical properties of 252P suggest a rather typical composition, yet somewhat enriched in methanol and ethane but low in formaldehyde (upper limit) compared to other short-period comets surveyed at infrared wavelengths. Analysis of the ortho/para ratio in water indicates a nuclear spin temperature larger than ∼38 K, consistent with statistical equilibrium (2σ). Spatial distributions of gases, which are representative of possible heterogeneity in the nucleus and/or gas dynamics upon sublimation, showed rather symmetric profiles, with subtle enhancements of the more volatile species C2H6 and HCN toward the sunward hemisphere, while water showed spatial distributions that were extended toward the anti-sunward hemisphere. The continuum was characterized by a narrow distribution. We place our infrared results in the context of observations with the Discovery Channel Telescope, the James Clerk Maxwell submillimeter Telescope, and the Hubble Space Telescope.

Comet 252P/LINEAR↗
NASA NTRS1990

IUE observations of comets P/Brorsen-Metcalf and Okazaki-Levy-Rudenko

Comet P/Brorsen-Metcalf (1989c) was observed with the International Ultraviolet Explorer (IUE) on several dates from 27 July 1989 through 5 August 1989; comet Okazaki-Levy-Rudenko (1989r) was observed in low dispersion with IUE on 2 and 22 December 1989. The water production rates for P/Brorsen-Metcalf were derived from OH measurements using the vectorial model of Festou (1981). Included also are the water production rates for Okazaki-Levy-Rudenko. Two estimates of the water production rate from the O I emission around 1304 A(octogons) are included. The ultraviolet continuum was not reliably measurable in comet P/Brorsen-Metcalf in most of the spectra, but Afp is approximately 30 cm for 2 August. For the comet Okazaki-Levy-Rudenko, an Afp = 50 cm was derived for 22 December. Both comets have very little dust compared to other recently observed comets. The ratio of CS to water production rates are presented. Relative to water, both comets had less CS than P/Halley in the same range of heliocentric distances. The CS production rates were obtained from a Haser model, assuming a short-lived parent (CS2). Because the dynamic range of the IUE spectrographs are limited, not all species can be measured in each spectrum. The P/Brorsen-Metcalf spectra from 31 July and 3 August were obtained from the NSSDC Archives. Due to the observing technique used for these spectra, the exposure time and hence, the brightnesses and derived quantities have a small uncertainty associated with them.

Roettger, E. E.↗
NASA NTRS2000

Spacewatch Survey of the Solar System

The purpose of the Spacewatch project is to explore the various populations of small objects throughout the solar system. Statistics on all classes of small bodies are needed to infer their physical and dynamical evolution. More Earth Approachers need to be found to assess the impact hazard. (We have adopted the term "Earth Approacher", EA, to include all those asteroids, nuclei of extinct short period comets, and short period comets that can approach close to Earth. The adjective "near" carries potential confusion, as we have found in communicating with the media, that the objects are always near Earth, following it like a cloud.) Persistent and voluminous accumulation of astrometry of incidentally observed main belt asteroids MBAs will eventually permit the Minor Planet Center (MPQ to determine the orbits of large numbers (tens of thousands) of asteroids. Such a large body of information will ultimately allow better resolution of orbit classes and the determinations of luminosity functions of the various classes, Comet and asteroid recoveries are essential services to planetary astronomy. Statistics of objects in the outer solar system (Centaurs, scattered-disk objects, and Trans-Neptunian Objects; TNOs) ultimately will tell part of the story of solar system evolution. Spacewatch led the development of sky surveying by electronic means and has acted as a responsible interface to the media and general public on this discipline and on the issue of the hazard from impacts by asteroids and comets.

McMillan, Robert S.↗
DOE OSTI2023

Simulations of Hypervelocity Impact Plasmas

The space environment is fraught with complex plasmas spanning a wide range of densities and temperatures. Much of space plasma research has focused on large-scale changes in the ambient plasma and fields from the Sun to the Earth’s atmosphere, driven primarily by the solar wind. Yet one particular type of space plasma, which forms from a hypervelocity impact (HVI), remains poorly understood. Hypervelocity impactors include both meteoroids and space debris. Meteoroids are naturally occurring objects in space that travel between 11 and 72.8 km/s and originate primarily from comets and asteroids. In contrast, space debris are human-made objects with speeds typically < 11 km/s. Hypervelocity impactors routinely hit spacecraft, yet the physics behind the formation of the plasma and the dynamics of its expansion remain largely unknown. The complexity of this phenomenon necessitates a research approach that includes both experimental studies and numerical simulation in order to understand the underlying physical processes that occur upon formation and expansion of the impact plasma. Our research has focused on providing a comprehensive understanding of plasma generated by hypervelocity impacts by meteoroids and space debris on spacecraft in order to characterize the behavior of the expanding plasma and its interactions with the ambient environment. Previously. we conducted experimental campaigns at a dust accelerator facility that can accelerate particles up to 60 km/s, which is representative of meteoroid speeds, and at a light gas gun facility that can accelerate larger projectiles up to 7 km/s, which is representative of orbital debris. The experiments included plasma, optical and radio frequency (RF) sensors in order to understand the dynamics and associated RF emission resulting from hypervelocity plasmas. For this research, we developed and applied machine learning algorithms to identify which type of impactor would produce RF and physics-based models to determine the source of the RF. This was a one-year research program that resulted in 2 refereed journal publications (uploaded separately).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1983

The Active Magnetospheric Particle Tracer Explorers program

In order to study the access of solar wind ions to the magnetosphere, together with the processes that transport and accelerate magnetospheric particles, the Active Magnetospheric Particle Tracer Explorers (AMPTE) mission will release and monitor lithium and barium tracer ions in both the solar wind and the magnetosphere. A single, massive release of barium in the dawn magnetosheath will in addition create a visible artificial comet in the flowing solar wind plasma, within which studies of a range of different plasma effects will be undertaken. The AMPTE will obtain comprehensive measurements of natural magnetospheric particle populations' elemental composition and dynamics. AMPTE comprises three spacecraft: the Ion Release Module, the Charge Composition Explorer, and the United Kingdom Subsatellite.

Krimigis, S. M.↗
NASA NTRS2001

Dynamic Finite Element Predictions for Mars Sample Return Cellular Impact Test #4

The nonlinear, transient dynamic finite element code, MSC.Dytran, was used to simulate an impact test of an energy absorbing Earth Entry Vehicle (EEV) that will impact without a parachute. EEVOs are designed to return materials from asteroids, comets, or planets for laboratory analysis on Earth. The EEV concept uses an energy absorbing cellular structure designed to contain and limit the acceleration of space exploration samples during Earth impact. The spherical shaped cellular structure is composed of solid hexagonal and pentagonal foam-filled cells with hybrid graphite-epoxy/Kevlar cell walls. Space samples fit inside a smaller sphere at the center of the EEVOs cellular structure. Pre-test analytical predictions were compared with the test results from a bungee accelerator. The model used to represent the foam and the proper failure criteria for the cell walls were critical in predicting the impact loads of the cellular structure. It was determined that a FOAM1 model for the foam and a 20% failure strain criteria for the cell walls gave an accurate prediction of the acceleration pulse for cellular impact.

Fasanella, Edwin L.↗
NASA NTRS1987

Solar wind effects on the outer ion coma of Comet Halley

A simple two-dimensional model is developed to examine the composition of the cometary ion coma in the region outside the ionopause which is strongly affected by the solar wind. Two-dimensional ion distributions are obtained assuming a cylindrically symmetric ion coma which accounts for the dynamic effects of the mass-loaded solar wind flow around the cometary ionosphere. The results of this model are discussed in the context of analyzing the GIOTTO ion data.

Flammer, K. R.↗
NASA NTRS1990

The Cosmic Dust Collection Facility on Space Station Freedom

The Cosmic Dust Collection Facility is an attached payload on board the Freedom Station that will serve as a long-term observatory of all dust-sized particles, typically of much less than 1 mm, either natural or man-made. Its instruments will measure the trajectories of individual hypervelocity particles and will trap the fragmented, melted or vaporized impactor residues in suitable capture media. The latter will be periodically returned to earth for detailed mineralogic and chemical characterization of these residues. The trajectory information will permit reconstruction of the astrophysical source(s) of natural dust grains, such that the compositional information may serve as proxy-analysis of primitive solar system objects among which comets and asteroids are known to be the most prolific dust sources. Trajectory information and chemical composition of man-made particles will yield clues about the most prolific anthropogenic sources. Direct measurement of the dynamic properties of all particles will contribute substantially toward an understanding of the collisional hazards to current and future space operations in LEO.

Horz, Friedrich↗
NASA NTRS2011

NASA Tech Briefs, July 2011

Topics covered include: 1) Collaborative Clustering for Sensor Networks; 2) Teleoperated Marsupial Mobile Sensor Platform Pair for Telepresence Insertion Into Challenging Structures; 3) Automated Verification of Spatial Resolution in Remotely Sensed Imagery; 4) Electrical Connector Mechanical Seating Sensor; 5) In Situ Aerosol Detector; 6) Multi-Parameter Aerosol Scattering Sensor; 7) MOSFET Switching Circuit Protects Shape Memory Alloy Actuators; 8) Optimized FPGA Implementation of Multi-Rate FIR Filters Through Thread Decomposition; 9) Circuit for Communication Over Power Lines; 10) High-Efficiency Ka-Band Waveguide Two-Way Asymmetric Power Combiner; 11) 10-100 Gbps Offload NIC for WAN, NLR, and Grid Computing; 12) Pulsed Laser System to Simulate Effects of Cosmic Rays in Semiconductor Devices; 13) Flight Planning in the Cloud; 14) MPS Editor; 15) Object-Oriented Multi Disciplinary Design, Analysis, and Optimization Tool; 16) Cryogenic-Compatible Winchester Connector Mount and Retaining System for Composite Tubes; 17) Development of Position-Sensitive Magnetic Calorimeters for X-Ray Astronomy; 18) Planar Rotary Piezoelectric Motor Using Ultrasonic Horns; 19) Self-Rupturing Hermetic Valve; 20) Explosive Bolt Dual-Initiated from One Side; 21) Dampers for Stationary Labyrinth Seals; 22) Two-Arm Flexible Thermal Strap; 23) Carbon Dioxide Removal via Passive Thermal Approaches; 24) Polymer Electrolyte-Based Ambient Temperature Oxygen Microsensors for Environmental Monitoring; 25) Pressure Shell Approach to Integrated Environmental Protection; 26) Image Quality Indicator for Infrared Inspections; 27) Micro-Slit Collimators for X-Ray/Gamma-Ray Imaging; 28) Scatterometer-Calibrated Stability Verification Method; 29) Test Port for Fiber-Optic-Coupled Laser Altimeter; 30) Phase Retrieval System for Assessing Diamond Turning and Optical Surface Defects; 31) Laser Oscillator Incorporating a Wedged Polarization Rotator and a Porro Prism as Cavity Mirror; 32) Generic, Extensible, Configurable Push-Pull Framework for Large-Scale Science Missions; 33) Dynamic Loads Generation for Multi-Point Vibration Excitation Problems; 34) Optimal Control via Self-Generated Stochasticity; 35) Space-Time Localization of Plasma Turbulence Using Multiple Spacecraft Radio Links; 36) Surface Contact Model for Comets and Asteroids; 37) Dust Mitigation Vehicle; 38) Optical Coating Performance for Heat Reflectors of the JWST-ISIM Electronic Component; 39) SpaceCube Demonstration Platform; 40) Aperture Mask for Unambiguous Parity Determination in Long Wavelength Imagers; 41) Spaceflight Ka-Band High-Rate Radiation-Hard Modulator; 42) Enabling Disabled Persons to Gain Access to Digital Media; 43) Cytometer on a Chip; 44) Principles, Techniques, and Applications of Tissue Microfluidics; and 45) Two-Stage Winch for Kites and Tethered Balloons or Blimps.

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